1. Field of the Invention
The present invention relates to a mobile terminal having an RFID (radio frequency identification) tag, the usage and importance of which have increased, and a detachable SIM (subscriber identification module), the usage and importance of which have also increased, and more particularly to a circuit in which an RFID tag is integrally coupled with an SIM, a mobile terminal circuit having the circuit and a method for performing an RFID function in a mobile communication terminal.
2. Description of the Related Art
An RFID transponder or a tag has been developed in an agriculture department of U.S. National Laboratory to identify livestock. The tag having an electric code capable of identifying an animal is inserted into or attached to the animal. In addition, an interrogator capable of interpreting such electrical code is installed in an animal stable, thereby conveniently checking whether the animal has returned to the stable. The interrogator transmits an RF signal to the tag, and the electric code stored in the tag is returned to the interrogator through a modulator of the tag. This is called a backscatter modulation. An RFID tag has an antenna coil through which a modulation signal is transmitted to the interrogator. Such systems are described in U.S. Pat. Nos. 4,075,632 and 4,360,810, the contents of which are incorporated by reference herein.
As RFID techniques make great strides, other techniques for identifying moving objects have been applied to various fields. For example, the techniques have been utilized for vehicles, ocean conveyance containers, or railroad vehicles. Information stored in a tag of such a transportation device is used for a location tracking, a content identification, and so forth. Techniques in relation to such fields are disclosed in U.S. Pat. Nos. 4,739,328, 4,782,345, 4,786,907, 4,816,839, 4,835,377, and 4,853,705, the contents of which are incorporated by reference herein.
Recently, the RFID technique has been tested in many kinds of fields. A communication system used in such fields has come into the spotlight, owing to wide applicability. For instance, since a mobile communication system has many subscribers, in a case where the mobile communication system employing new techniques such as RFID is industrialized, it is possible to easily make profits. Also, since a current mobile communication is stabilized in the aspect of profitability, vendors request to develop applications capable of making supplementary value.
FIG. 1 shows a structure of a passive RFID tag. A tag shown in FIG. 1 is MCRF200 available from Microchip Technology, Inc.
A modulation circuit 209 is a part for connecting antenna coils (not shown) to RFID circuit elements. As an RFID interrogator (not shown) approaches an RFID tag, according to Faraday's law, the antenna coil generates induced electromotive force through an inductive coupling between the RFID interrogator and the RFID tag. Voltage intensity of the antenna coil varies depending on a modulated signal outputted from the modulation circuit 209.
A rectifying section 202 rectifies AC voltage of the induced electromotive force in order to supply DC voltage to other components. A clock generating section 201 generates a system clock by extracting carrier frequency from a signal transferred from the RFID interrogator. The clock generating section 201 supplies other circuit components of the RFID tag with a baud rate, a modulation rate, and a programming rate. A row decoder 204 and a column decoder 207 extract ID data stored in a memory 206 at a clock rate and encode an extracted ID data by means of an NRZ (Non Return to Zero) Direct method, a Differential Biphase method, or a Manchester Biphase method before modulation, thereby generating a serial data stream.
A modulation control section 203 modulates the serial data stream transferred from the decoders 204 and 207 by using a predetermined method, such as an FSK (Frequency Sift keying) method or a PSK (Phase Shift Keying) and the like, and transfers the serial data stream to the modulation circuit 209. A counter 205 counts clocks outputted from the clock generating section 201, so as to provide the clocks to the row decoder 204 and the column decoder 207.
In a case in which a mobile communication system employs an RFID technique, it is expected to provide various supplementary services suitable for cellular systems. In this case, it is absolutely necessary that current RFID equipment are properly combined with current cellular systems. It has already mentioned that an RFID tag (e.g., a card-type RFID tag) is combined with an existing mobile terminal. An example of the RFID tag is disclosed in Korean Patent laid-open publication No. 2002-0090929 entitled “mobile communication terminal apparatus”.
However, since a generally-used RFID tag is only provided for an existing mobile terminal circuit without modifying it or performing an adaptation process, the problem occurs that such an RFID tag is not adaptable for the miniaturization and portability of the existing mobile terminal which are essential features of a mobile terminal.
Meanwhile, a mobile telephone having a GSM (Global System for Mobile telecommunication) mode generally uses a SIM card for identifying subscribers. The SIM card has a small-sized card shape and is used while being set in a slot provided on a rear side of a body of a GSM mode mobile telephone.
FIG. 2 shows a structure of a conventional SIM card for a mobile terminal.
A SIM card used for mobile communication systems, such as GSM systems, is defined in GSM 11.11 Standard, GSM 11.12 Standard, and ISO/IEC 7816. In these standard documents, physical characteristics and electrical signals and transmission protocols of the SIM card and a logical model for the SIM card are explained. The SIM card has 8 external pins. Contact pins C1, C2, C3, C5, and C6 refer to voltage Vcc, a reset RST, a clock CLK, a ground GND, and program voltage Vpp, respectively. A contact pin C7 is an external pin for data input/output I/O and is connected to an antenna for identifying radio frequency. Also, contact pins C4 and C8 RFUs are reserved.
The SIM card internally has a Read Only Memory (ROM) 304 including an operation system operating the SIM card, a Central Processing Unit (CPU) 300 controlling an SIM card operation, a Random Access Memory (RAM) 302 which is a data processing block, and an Electrically Erasable Programmable Read Only Memory (EEPROM) 306 storing identity information of the SIM card.
The SIM card is a kind of a smart card. If an RFID tag having functions of the smart card is separately provided for a mobile communication terminal capable of detaching the SIM card, wasteful factors occur. If the SIM card and the RFID tag are separately provided for the mobile communication, it is difficult to manage the RFID tag for service vendors, who provide various services using the SIM card and pursue added value creation through the various services. Accordingly, it is impossible for the service vendors to acquire the expected advantages resulting from employing the RFID tag, which are namely an increase of profit by means of an RFID service, an increase of the number of subscribers, and an expansion of a service range.
There exists a method in which the SIM card provides additional functions besides a primary function for authenticating mobile terminal users. For instance, a SIM/WIM card which achieves a WIM (Wireless Application Protocol Identify Module) function for providing application services is formulated as WAP Provisioning Smart Card WAP-186-PROVSC-20010710-a Version by the WAP forum. Toolkit applications providing additional services by dynamically using the SIM card are defined in the GSM 11.14 Standard.
The above-mentioned forum or standards only defines file structures and protocols for providing application services, and do not define hardware or software protocols accompanied with combination or connection between the RFID tag and the SIM card. Also, the above-mentioned forum or standards do not solve all existing problems.